1. Field of the Invention
The present invention generally relates to heat transfer devices. More specifically, the present invention is drawn to an economizer unit for a heat recovery steam generator (HRSG).
2. Description of the Related Art
Maintaining the integrity of water tubes in heat recovery systems has been problematic in that the tubes are subjected to high mechanical stresses due to thermal expansion and contraction. Load changes, frequent stops and starts, water temperature differential, etc., all contribute to stresses that can lead to the degradation of the tubes. Leaking tubes usually require shutdown of the system so that the degraded tubes can be replaced. Such shutdowns obviously result in economic loss. Heretofore, attempted solutions to prolong the life of the tubes have included adding bends to the tubes, increasing the size and radius of existing bends, adding a re-circulation system or just accepting tube leaks and repairing them as they occur. These solutions have proven to be uneconomical, especially since leaks are not easily anticipated. The art would certainly welcome an uncomplicated and efficient economizer design that would alleviate the above discussed problems.
There are many economizer designs described in the related art. Pertinent examples of such related art are cited and described in the accompanying IDS. However, none of the above cited and described related art, taken either singly or in combination, is seen to disclose an economizer as will be subsequently described and claimed in the instant invention.